Construction vehicles, such as hydraulic excavators, normally employ a plurality of double-acting hydraulic cylinders thereon to selectively actuate various implements thereof. For example, such a cylinder is normally pivotally interconnected between a frame of the excavator and a boom thereof, pivotally mounted on the frame, to selectively raise or lower the boom relative to ground level. Upon lowering of the boom, for example, it is desirable to prevent such lowering at too rapid a pace and to further prevent any cavitation in the cylinder.